1. Field of the Invention
The invention relates to the field of animal caging systems having removable enclosures for isolating one or more animals while providing for the supply of air and water, and facilitating access such that the animals can be serviced, e.g., to change bedding or to place food in the cage. The invention is apt for high density housing arrangements such as in testing laboratories, that house many animals in a compact space. Cage boxes, for example of molded plastic, have quick-connect water fittings that engage or release with displacement of a sleeve. The cages have lids with a fibrous air-permeable membrane stretched over a frame, and an actuator mounted in the frame is arranged to release the quick-connect fitting for each cage by manual action from the opposite side of the cage.
2. Prior Art
It is known to house animals such as laboratory mice, rats, rabbits, cats and the like, in cage rack systems having enclosures for individual animals or groups of animals disposed in close proximity. In addition to providing space for the animals, the enclosures isolate the animals from contagion originating with other animals or with human personnel, or perhaps quarantine animals who are contagious either to one another or to humans. Animals are housed in box enclosures, for example of clear polycarbonate, which are airtight on their sides and bottoms and fit against the undersides of internally ducted shelves for the supply of air. When the animals are serviced, the enclosures are removed from the rack and serviced in a work area that can also have enclosure means, a protected air supply, etc.
A source of contagion in such animal housing systems is the airborne dust and dander that the animals produce. To minimize the exposure of the animals to airborne contagion from other animals, the air supply can be filtered and the cage boxes or enclosures can be covered in a manner that permits airflow. In U.S. Pat. Nos. 4,343,261; 4,402,280; and 5,044,316, all to Thomas, airtight lids are sealed over the boxes and are provided with spring biased valves that are opened by contact with the rack as the cage is slid under a rack shelf. The valves open an airflow path through the supply and exhaust ducts, for coupling the internal volume of the cage to the air supply. When the cage is removed from the rack, the valves close and isolate the cage volume in an airtight manner. The cage can be opened in a protected environment for servicing.
Thomas '261 and '316 have individual valve bodies operable by downward pressure from the underside of a ducted shelf. Thomas '280 has a single sliding valve body that covers or uncovers all the valve openings, operable by pressure against a flange or stop encountered when the cage is fully inserted into place. Thomas '316 has a valved cage cover comprising an air permeable fibrous filter membrane, rather than airtight valved covers as in Thomas '261 and '280. Air diffuses through the cover when the cage is removed, so the levels of oxygen, ammonia and the like are less affected when the cage is removed and the valves close, than with an airtight cover. The disclosures of the Thomas patents are incorporated herein in their entireties.
Other animal housing systems having cage enclosures covered by filter material include U.S. Pat. Nos. 3,343,520--Schwarz, Jr.; 3,528,277--Lee et al; 4,480,587--Sedlacek; and British Patent 2,065,440--Bernardini. Typically, filter-covered cages are exposed to the open air rather than coupled to racks with internal air ducts.
In addition to air, the animals of course require food and water. Water can be supplied from a water bottle held in a depression in a wire grid disposed in the cage, having a nozzle depending into the cage area. The wire grid can also have a food compartment allowing the animals to obtain food by pulling it through spaces in the wire grid. An internal water bottle requires servicing including washing and refilling. It is desirable to provide a piped water supply to the cages to avoid the need for such service.
Water supply arrangements are disclosed, for example, in U.S. Pat. Nos. 4,989,545--Sheaffer et al; 5,000,120--Coiro, Sr. et al; 5,042,429--Deitrich et al; 5,148,766--Coiro, Sr. et al; and 5,165,362--Sheaffer et al, which are hereby incorporated. The nozzle of the water fitting typically is operable by the animals and can have a movable valve body. It is possible to provide a water nozzle or other outlet that is permanently attached and protrudes from a supply line to be received through an opening in the cage box as in Coiro '120. This is not preferred because an opening is left in the cage box when the cage box is removed from the rack for service, risking the ingress or egress of contagion. The water fitting also can become a source of cross contamination, namely if a different cage box is inserted into a given rack position after servicing. Therefore, a better technique is to attach the nozzle permanently to the cage box and to provide a water connection fitting that attaches the nozzle to the water supply when the cage is inserted into the rack, thereby opening a valve to the water supply. An example is shown in Deitrich '429.
The water connection fitting couples the water supply to the nozzle and the nozzle traverses the otherwise-airtight wall of the cage. The water connection fitting needs to close off the water supply tightly when the nozzle (which has its own valve) is removed and therefore is unavailable to provide a closure that prevents leakage. It is desirable that the water connection fitting provide a positive opening and closing action. However, the water connection fitting is located behind the cage box in the direction of insertion of the cage into the rack, and is inaccessible. It may be difficult to achieve a positive connection when inserting the cage box, which is done mostly by feel. If a water connection coupling is provided that has a very positive connection/disconnection action, it is typically difficult to disengage the water connection fitting when removing the cage box. As a result, water connection fittings are less positive than they could be, typically having a relatively loose spring biased arrangement urging a valve body to close, the valve body being displaced upon insertion of a cylindrical protrusion of the nozzle on the rear of the cage box.
Positive quick-coupling structures are known, for example in fittings for pressurized air lines. A female part on the supply side has an axially movable valve body that rests against a seat to close the valve. The valve body is pushed back from the seat by a complementary male part to open the valve. The male part has an annular groove near its distal end. The female part has several ball bearings or the like in a race providing for limited radial displacement clearance for the bearings. The bearings reside in the groove of the male part when the fitting parts are engaged, locking the male part to the female part against being blown off with pressure or inadvertently pulled apart.
A sliding collar on the female part has a smaller inside diameter portion and a larger inside diameter portion at different axial positions along the collar, the collar being axially movable either to position the smaller or larger diameter portion over the bearings. The smaller diameter portion normally holds the bearings radially inwardly, i.e., in the groove of the male part when the fitting is attached. When the collar is pushed back against axial spring bias, the larger diameter portion allows the ball bearings to be displaced radially outwardly from the groove in the male part such that the male and female parts can be attached or detached freely.
Although the collar can be tapered between the larger and smaller inside diameter portions and/or the distal end of the male part can be tapered, the annular groove of the male part is closely complementary to the bearings, as needed to lock the male and female parts together. If the male and female parts are pulled axially when locked together, there is no tendency for the collar to become displaced. Upon insertion of the male part, the locking of the bearings in the groove is perceptible to the user as a satisfying snap engagement that positively fixes the fitting.
Less positive fittings are possible for water connection fittings in animal caging systems. For example, instead of a locking collar, a resilient band can be used to bear inwardly on the male fitting. A structure having radially biased bearings or other locking structures can engage a tapered annular groove in the male member. The groove can have tapered walls, etc. Such features would enable the fitting to be engaged and disengaged simply by axial pressure to push the fittings together or pull them apart. A less-positive engagement, however, is likewise less effective for coupling together the parts.
It would be desirable to employ a positive water connection fitting in an animal caging system, for example using a structure similar to the foregoing pneumatic type fitting with an axially displaceable collar. However, positive fittings typically require manual displacement of a part such as the collar of the female fitting. Both fittings are inaccessibly located at the rear side of a cage box being inserted into the rack by the user, which may be the only practical place for such a fitting in view of the path of the cage box upon insertion and removal. The user cannot easily operate the release mechanism of such a fitting. It is an aspect of the present invention to resolve these matters by providing a displaceably means in the lid of the cage box that the user on the opposite side of the cage can use to manipulate the release means of the water connection fitting for conveniently engaging and disengaging the water connection in a positive manner.